Funds are requested for the purchase of a STEM/SEM attachment for a JEOL JEM-1200EX electron microscope and for a computer system to be coupled to the electron microscope for use in direct image analysis. The Computer-Coupled Electron Microscope will be used by several investigators in the Columbia University Department of Biological Sciences whose scientific interest lie primarily in the areas of Cellular and Developmental Neurobiology. The projects that will require the use of this instrument include studies of: (1) the molecular structure of acetylcholine receptors, (2) the ultrastructure of developing rat neuromuscular junctions, (3) the effects of specific mutations on the ultrastructure of sensory cells in the nematode Caenorhabditis elegans, (4) the action of androgens in the sexual differentiation of neurons and muscles in Xenopus, and (5) the synaptic circuitry underlying processing of sensory information in arthropods and fish. An important aspect of this work will be the computer-aided analysis of serial electron images. The 3-D reconstruction of neurons and their synaptic connections will be carried out using existing hardware and software developed for this purpose in the Department's Computer Graphics Facility.